Sewing machine



H. w. KRAG 2,337,252

SEWING MACHINE Filed OGt. 1, 1941 2 Sheets-Sheet 1 Dec. 21, 1943. H. w. KRAG 2,337,252

' SEWING MACHINE Filed 001.. 1. 1941 2 Sheets-Sheet 2 Patented Dec. 21, 1943 SEWING MACHINE Harry American St. Louis, Mo., a corpora W. Krag, Vinita Park, Mo., assignor to Shoe Machinery and Tool Company,

tion of Missouri Application October 1, 1941, Serial No. 413,103

'7 Claims.

This invention relates to sewing machines, particularly shoe sole sewing machines of the kind provided with means for intermittently locking the presser foot on the work during sewing. The invention has for its principal object to provide a simple and efiicient smoothly and quietly operating mechanism for automatically clamping and unyieldingly locking the presser foot on the work; to provide for varying the clamping action prior to locking the presser foot on the work; and to provide for automatically clamping the presser foot during the forming of the first stitch. The invention consists in the sewing machine and in the construction, combinations and arrangements of parts hereinafter de scribed and claimed.

In the accompanying drawings, which form part of this specification and wherein like symbols refer to like parts wherever they occur,

Fig. 1 is a fragmentary side elevational view of the stitcher head portion of a sewing machine embodying my invention, the presser foot being shown in locked position,

Fig. 2 is a fragmentary top plan view, partly in horizontal section, of the portion of the machine shown in Fig. 1,

Fig. 3 is an enlarged fragmentary side elevational view, similar to Fig. 1, showing the presser foot in unlocked position.

, Fig. 4 is a top plan view of the portion of the machine shown in Fig. 3; and

Fig. 5 is a vertical sectional view on the line 5-5 in Fig. 3.

In the accompanying drawings, my invention is embodied in a shoe sole sewing machine comprising a stitcher head I having an upwardly and forwardly extending lug 2 on the front face thereof, a lever 3 pivotally supported on a pivot pin 4 fixed to said lug. and a presser foot 5 fixed to the forward end of said lever and adapted to press the work 6 down on a support I. A feed slide 8 reciprocates in a slideway 9 in said stitcher head and carries the usual awl (not shown) for piercing and feeding the work. The machine also includes the usual thread measuring yoke I I, which is pivotally connected, as at l2, to the rear arm of the presser foot lever 3, and a spring I3, which is interposed between the stitcher head I and said yoke and operates at all times to swing said lever in a direction that will cause the presser foot thereon to press the work 6 down on the work support I. The presser foot lever 3 has an upstanding handle l4 fixed to its outer arm, whereby said lever may be manually operated to raise the presser foot 5 off the work. The construction of sewing machine hereinbefore described is well known and it is considered unnecessary to illustrate it in detail.

As shown in the drawings. the rear arm of the presser foot lever 3 terminates in an arcuate rack l5 which intermeshes constantly with a pinion l6 for locking said lever against swinging movement. This lock pinion is preferably formed integral with a friction wheel or brake drum I'I journaled on a pivot stud l8 fixed to an arm I9 that is pivoted at one end on a stud 20 fixed to the stitcher head I rearwardly of the rear end of the presser foot lever 3 and extends forwardly alongside thereof. As shown in the drawings, the pivoted end of the arm I9 is provided with an eccentric bushing 2 I, which may be rotated in said arm to obtain the proper depth of immeshment of said pinion and the-arcuate rack I5 at the rear end of the presser foot lever 3. The bushing H is locked in the arm I9 in the desired position of rotary adjustment by means of a clamp screw 22 threaded through the split bushing receiving end of said arm. Mounted on the free forward end of the brake wheel and lock pinion supporting arm I9 is an adjustable stop screw 23 that is threaded downwardly through said arm with its lower end in abutting relation to a suitable abutment pin 24 fixed to the stitcher head I. The stop screw 23 may be adjusted to properly position the arm and is locked in the desired position of adjustment by means of a clamp screw 25 threaded through the split screw receiving end thereof. A coiled tension spring 26 has one end anchored to an upstanding pin 21 on the stitcher head I and its other end secured to a depending lug l9a on the pivoted end of the arm I9 and thus serves to swing said arm upwardly and thus bring the adjustable stop screw 23 at the free end thereof into abutting relation with the abutment pin 24.

Located rearwardly of the brake wheel or drum (1, for swinging movement into and out of engagement with the peripheral surface thereof, is a brake arm or shoe 28. This brake shoe is rotatably mounted on the eccentric bushing 2| and is held thereon between the arm I9 and a head 2Ia formed on the outer end of said bushing. A bent lever or crank 29 is pivotally supported on an outstanding pivot stud 30 fixed to the stitcher head I below pivotal brake arm or shoe I9. The front arm of the crank 29 inclines forwardly and upwardly and is pivoted, as at 3|, to the lower end of a link 32, whose upper end is pivotally connected. as at 33, to the free, lower end of the brake shoe 29, said link forming an elbow or knee-joint between said arm of said crank and said brake shoe. The crank 29 is held on its supporting pivot 30 by means of a washer 34 that is removably secured to the outer end of said pivot by means of a screw 35.

An arm 36 is pivotally supported at one end on a pivot pin 31 fixed to the stitcher head I rearwardly of the crank 29. The arm 36 extends forwardly from its pivot 31 and has a cam roller 38 journaled thereon between the ends thereof that works in a suitable cam groove 39a provided therefor in a face cam 39 fixed to a horizontal shaft 46 journaled in a suitable bearing (not shown) provided therefor in the stitcher head. The forward end portion 36a of the cam roller supporting arm 36 has a stud 42 mounted in its free end; and said stud has an eccentric pin 43 on the inner end thereof that overhangs the rear arm of the crank lever 29. A coil tension spring 44 has one end connected to the rearwardly extending arm of the crank lever 29 and its other end anchored to a pin 45 fixed to the downwardly inclined eccentric pin supporting forward end of the cam roller supporting arm 36 and operates to swing said crank lever on its pivot until the rear arm thereof abuts against the underside of the eccentric stop pin 43 on the stud 42 carried by said cam arm. The stud 42 may be rotated in the arm 36 to vary the position of the eccentric stop pin 43 relative to the rear arm of the crank lever; and the stud receiving end of said arm is split and provided with a clamp screw 49 for locking said stud in the desired position of rotary adjustment.

In operation, the cam arm 36 is oscillated by the face cam 39 and the rear arm of the crank 29 is depressed at the lowest position of said cam arm (see Fig. 3) which action breaks the straight line toggle (see Fig. 1) formed by the link 32 and the forward arm of said crank, thus releasing from the brake wheel [1 the brake arm 29 controlled by said link and freeing the pinion I6 and presser foot lever 3 locked thereby and permitting the presser foot on the forward end of said lever to rise or fall to conform to the thickness of the work. In this position of the parts, (see Fig. 3) the stop screw 23 at the outer end of the lock pinion and brake wheel supporting arm [9 abuts against the fixed abutment pin 24 and the pivotal brake shoe 28 is clear of the brake wheel 11, whereby the presser foot 5 may be raised against the force of the spring I3 interposed between the stitcher head and the thread measured yoke ll pivotally connected to the rear arm of the presser foot lever 3. This spring l3 exerts the normal pressure on the work and tends, at all times, to force the presser foot downwardly.

In the cycle of operations, the locking mechanism is in the position shown in Fig. 3, in which position the presser foot is under the influence of the spring l3 at the time of feeding. After the feeding of the work has taken place, the cam arm rises and the toggle connection formed by the forward arm of the crank 29 and link 32 straightens out and brings the pivots 39, 3| and 33 in a straight line, as shown in Fig. 1, thereby swinging the brake shoe 26 into engagement with the peripheral surface of the brake wheel 11 and taking up all looseness in the connections, and then swinging the brake wheel supporting arm I 9 upwardly. The pinion [6, being frlctionally held from rotation, then raises the rear arm of the presser foot lever 3, thereby causin the ward arm thereof to swing downwardly and bring the presser foot 5 into engagement with the work. During this action, the stop screw 23 is raised from the abutment pin 24 and the presser foot; 5 is locked against the straightened toggle formed by the link 32 and the forward arm of the crank lever 29. Thus, the mechanism is self-locking whenever the stop screw 23 on the arm 19 is raised clear of the abutment pin 24; and said stop screw provides an adjustment for increasing or decreasing the clamping pressure so that it is possible to retract said screw and apply the full action of the locking shoe 29 or to advance said screw and lock the presser foot 5 with slight clamping pressure. The eccentric stop pin 43 on the stud 42 carried by the cam arm 36 permits the crank lever 29 to be adjusted relative to the brake shoe 28 so that the toggle connection therebetween will provide a line look when said shoe is applied. The spring 44 holds the crank 29 in contact with said pin, thereby preventing hammering of said arm on said pin and thus rendering the mechanism quiet in operation.

Pedal operated mechanism is provided for releasing the presser foot lock and for raising the presser foot so as to permit the work to be inserted in and removed from the machine. This mechanism comprises a release lever 41 supported on a pivot 48 mounted in an upwardly extending brace or arm 49 on the end of the presser foot lever pivot 4, swinging movement of said release lever being limited by an abutment surface 50 provided on said brace. The lower arm of the release lever is urged forwardly into engagement with the abutment surface 50 by a coil tension spring 5| suitably connected to said lever and to a pin 52 fixed to the brace 49. A cam lever 53 is pivotally mounted, as at 54, on the lower arm of the release lever 41 and has a convex cam surface 55 at its forward end that engages an abutment pin 56 fixed to the brace 49 when the rear arm of said cam lever is depressed.

The rear end of the cam lever 53 is pivotally connected, as at 51, to an upright link 58 having a hook 59 at its upper end. this hook link being normally raised so as to hold the cam lever 53 in the position shown in Fig. 1. The lower end of the hook link 58 is pivotally connected. as at 69, to the forwardly extending arm of a lever 6| pivoted on a stud 62 secured to the stitcher head. A normally raised upright pull rod or link 63 is suitably connected, as at 64, at its upper end to the lever 61 and is pulled downwardly by means of a pedal (not shown) connected to the lower end thereof. When the hook link 59 is depressed, the convex cam surface 55 of the cam lever 63 engages the fixed abutment pin 56 on the brace 49 and forces the lower, cam lever supporting arm of the release lever 41 rearwardly. This arm of the release lever 41 is pivotally connected, as at 65, to the forward end of a release link 66 whose rear end is bifurcated, as at 61, to straddle the stud 3! that pivotally connects the toggle link 32 to the forward arm of the crank lever 29, whereby said release link. when forced rearward 13 by said release lever, breaks the toggle formed by said link and crank, thereby releasing the brake shoe 28 from the brake drum l1 carried by the pivotal arm 19. Further downward travel of the hook link 59 causes the hook 59 at the upper end thereof to engage a, stud 6B fixed to the rear arm of the presser foot lever 3, thereby depressing said arm Of said lever and raising the front arm thereof and lifting the presser foot oil" the work.

When the presser foot 5 is thus raised to lay the work 6 on the table 1 and then lowered, the presser foot is clamped on the work by the force of the comparatively light spring I3. When making the first stitch, it is customary for the operator to seat the work by a downward pull on the upstanding handle M on the forward arm of the presser foot lever 3, at which setting the presser foot 5 is locked. In previous constructions auxiliary pressure means is provided for applying added pressure to the work just before looking the presser foot, but such pressure is applied at the end of the work feed for the first stitch and not while the first stitch is being formed. In the present locking mechanism, however, the clamping and locking action is the same when the toggle is actuated by the cam arm 36 or by the manual release; because, when the brake shoe 28 is released, the lock lever l9 moves to set position and the presser foot 5 rests on the work. As the toggle is permitted to straighten out, the brake shoe 28 contacts the brake drum l1 and then raises the lock lever l9, together with the lock pinion I6, which action clamps the work. When the crank lever 29 and link 32 form practically a straight line connection between said crank lever and said brake shoe, the presser foot 5 is firmly locked on the work 5. This clamping pressure is determined by the movement of the lock lever l9, and this movement is determined by adjustment of the stop screw 23. The clamping and locking action is thus automatic and the presser foot is locked whenever the lock lever I9 is supported by the brake shoe 2B and is released whenever sa d lever is supported by the adjustable stop screw 23. This step screw 23 provides adjustment so that the presser foot may be merely locked against upward movement, or said stop screw may be set so as to apply considerable clamping pressure on the work.

What I claim is:

1. In a sewing machine, a work support, a presser foot, and automatic means for pressing said presser foot against the work, said means including a toggle joint adapted when approaching a straight line position to press said presser foot against the work and then lock said presser foot in pressing position, a spring for urging said toggle to such straight line position and a cam lever operating against the force of said spring for breaking said toggle, and separate manually operated means operable against the force of said spring for breaking said toggle joint to unlock said presser foot, release said pressure and then move said presser foot far enough away from said work support to permit insertion or removal of the work.

2. In a sewing machine, a work support, and mechanism for pressing the work down on said work support, said mechanism comprising a presser foot lever pivotally supported on said machine and having a presser foot at one end thereof and a rack at the opposite end thereof, a lock arm pivotally supported on said machine, a pinion journaled on said lock arm and intermeshing with said rack, a brake wheel journaled on said arm for rotation with said pinion, a brake shoe plvotally supported on said machine for swinging movement into and out of engagement with said brake wheel, and a tog le joint operatively connected to said brake shoe and adapted during movement towards straight line position to swing said brake shoe into braking engagement with said brake wheel to thereby lock said pinion to said rack, and then swing said lock arm and the locked pinion carried thereby in a direction that will swing said presser foot lever on its axis and press the presser foot against the work.

3. In a sewing machine, a work support, and mechanism for pressing the work down on said work support, said mechanism comprising a presser foot lever pivotally supported on said machine and having a presser foot at one end thereof and a rack at the opposite end thereof, a lock arm pivotally supported on said machine, a pinion journaled on said lock arm and intermeshing With said rack, a brake wheel journaled on said arm for rotation with said pinion, a brake shoe pivotally supported on said machine for swinging movement into and out of engagement with said brake wheel, and a cam actuated toggle joint operatively connected to said brake shoe and adapted during movement towards straight line position to swing said brake shoe into braking engagement with said brake wheel to thereby lock said pinion to said rack, then swing said lock arm and the locked pinion carried thereby in a direction that will swing said presser foot lever on its axis and press the presser foot against the work, and then look said presser foot lever in such position.

4. In a sewing machine. a work support, and mechanism for pressing the work down on said work support, said mechanism comprising a presser foot lever pivotally supported on said machine and having a presser foot at one end thereof and a rack at the opposite end thereof, a lock arm pivotally supported on said machine, a pinion journaled on said lock arm and intermeshing with said rack, a brake wheel journaled on said arm for rotation with said pinion, a brake shoe pivotally supported on said machine for swinging movement into and out of engagement with said brake wheel, and a cam actuated toggle joint operatively connected to said brake shoe and adapted during movement towards straight line position to swing said brake shoe into braking engagement with said brake wheel to thereby lock said pinion to said rack, then swing said lock arm and the locked pinion carried thereby in a direction that will swing said presser foot lever on its axis and press the presser foot against the work, and then lock said presser foot lever in such position, and separate nonautomatic means for breaking said toggle to release said hrake shoe and presser foot lever.

5. In a sewing machine, a work support, and mechanism for pressing the work down on Said work support, said mechanism comprising a presser foot lever pivotally supported on said machine and having a presser foot at one end thereof and a rack at the opposite end thereof, a lock arm pivotally supported on said machine, a pinion journaled on said lock arm and intermeshing with said rack. a brake wheel journaled on said arm for rotation with said pinion, a brake shoe pivotally supported on said machine for swinging movement into and out of engagement with said brake wheel, and a cam actuated toggle joint operatively connected to said brake shoe and adapted during movement towards straight line position to swing said brake shoe into braking engagement with said brake wheel to thereby lock said pinion to said rack, then swing said lock arm and the locked pinion carried thereby in a direction that will swing said presser foot lever on its axis and press the presser foot against the work, and then look said presser foot lever in such position, and separate non-automatic means for breaking said toggle to release said brake shoe and presser foot lever, and then swing the latter in a direction that will move the presser foot far enough away from said work support to permit easy insertion or removal of the work.

6, In a sewing machine, a work support, and mechanism for pressing the work down on said work support, said mechanism comprising a presser foot lever pivotally supported on said machine and having a presser foot at one end thereof and a rack at the opposite end thereof, a lock arm pivotally supported on said machine, a pinion journaled on said lock arm and intermeshing with said rack, a brake wheel journaled on said arm for rotation with said pinion, a brake shoe pivotally supported on said machine for swinging movement into and out of engagement with said brake wheel, and a cam actuated toggle joint operatively connected to said brake shoe and adapted during movement towards straight line position to swing said brake shoe into braking engagement with said brake wheel to thereby lock said pinion to said rack, then swing said lock arm and the locked pinion carried thereby in a direction that will swing said presser foot lever on its axis and press the presser foot against the Work, and then look said presser foot lever in such position, and independently adjustable stops for limiting the opening and closing movements, respectively, of said toggle joint.

7. In a sewing machine, a work support, and a mechanism for pressing the work down on said work support, said mechanism comprising a. presser foot lever pivotally supported on said machine and having a presser foot at one end thereof and a rack at the opposite end thereof, a lock arm pivotally supported on said machine, a pinion journaled on said lock arm and intermeshing with said rack, a brake wheel journaled on said arm for rotation with said pinion, a brake shoe pivotally supported on the lock arm pivot for swinging movement into and out of braking engagement with said brake wheel, a mechanically actuated crank lever pivotally mounted on said machine, a link connecting said brake shoe with one arm of said crank, said link and crank lever arm constituting a toggle joint connection between said brake shoe and crank lever adapted during movement towards straight line position to swing said brake shoe into braking engagement with said brake wheel to thereby lock said pinion to said brake, then swing said lock arm and the locked pinion thereon in a direction that will swing said presser foot lever on its axis and press said presser foot against said work, and then look said presser foot lever in said position, adjustable means for limiting the straightening movement of said toggle joint, adjustable means for limiting the closing movement of said toggle joint, and non-automatic means for braking said toggle joint and for swinging said presser foot lever in a direction that will lift said presser foot entirely clear of the work.

HARRY W. KRAG. 

